This invention relates to a method of, and apparatus for, applying collars of aluminium sheet or the like onto the nipples of anode bars projecting from anode blocks.
The carbon anode blocks used for the electrolytic extraction of aluminium are arranged on anode bars. Each anode bar has a so-called spade provided with nipples. The nipples are set in nipple holes in an anode block and are fixed in them, for example by casting (see EP-A No. 150 680). The nipple ends projecting from the nipple holes have to be protected against corrosion and consumption. For this purpose, a strip of aluminium sheet metal, which is bent into a collar shape and is closed by means of a hook fastener, is placed around each of the nipples. The space between each protective collar and its nipple is then filled with a granular composition. In use, the aluminium collars melt away fairly quickly, so that the granulate, which is sintered to a compact protective composition, protects the nipples.
The collars are usually applied by hand, as is the introduction of the granulate, although a mechanical filling device has been proposed for this purpose (see EP-A No. 121 954).
The aim of the invention is to provide a method of, and apparatus for, applying sheet metal collars onto the nipples of anode bars, which enable collars to be positioned mechanically in an economical and reliable manner so that the time-consuming, complicated manual work (which is also unpleasant due to the degassing of the granulate or is even harmful to health), and was formerly necessary, can be dispensed with.